Rough average clickthrough ratio for FB ads (assuming we're including all the people who are Doing Advertising Wrong) is about .08%, so on average FB users are

Rough average clickthrough ratio for FB ads (assuming we're including all the people who are Doing Advertising Wrong) is about .08%, so on average FB users are clicking one ad in every 1250 they see. 5 ads per page, ish, so that's one click per 250 pages viewed. Meanwhile, CPC for Facebook ads is much higher than 2 cents - or I'd be spending a lot more money there. $.2 - $.4 is more common. So assuming a FB user checks an average of 10 pages a day (which sounds about right, given, say, a few profile refreshes, a couple of message replies, a photo or two, maybe a game) that's 3000 page views approx over a year, which is 15000 ad views, giving us about 12 clicks at about $.3 each, for a customer value per year of closer to $4 or so. Having said that, $5 per year still isn't very much to pay...